The present invention relates to a method and apparatus for regulating or adjusting the operation of machines for the production of smokers' products. More particularly, the invention relates to improvements in a method and apparatus for regulating the operation of machines for the production of a continuous rod which can be subdivided into rod-shaped articles constituting or forming part of smokers' products. Such machines include those which manufacture plain cigarettes, cigars or cigarillos and filter rod sections. Still more particularly, the invention relates to a method and apparatus for processing signals which denote a selected characteristic (for example, density) of successive predetermined lengths of a moving rod of fibrous material in a machine of the above outlined character.
It is already known to monitor the rod which is formed in a cigarette making machine and is about to be subdivided into plain cigarettes of desired length. The monitoring step can involve ascertainment of density of successive unit lengths of the rod. The resulting measurement (density) signals are thereupon converted into signals which are useful to the attendants for appropriate adjustment of the machine in the event that the results of the monitoring operation indicate the need for adjustment. As a rule, signals which represent the density of unit lengths of the moving rod are converted into signals denoting the standard deviation (sigma) of the weights of cigarettes from a desired or optimum value. Such mode of monitoring the quality of the rod is not entirely satisfactory because all the attendants can ascertain is the statistical deviation of individual weights Xi from the average weight X of a given group of N cigarettes. Thus, signals which denote the standard deviation (sigma) do not indicate the extent of deviation of the average weight of a group of cigarettes or the like from the desired average weight. Such deviation of average weight must be ascertained in addition to the aforediscussed determination of standard deviation. In order to be capable of evaluating the range of tolerances as well as the relationship of such tolerances to the desired weight of cigarettes or the like, the person in charge of a cigarette making or like machine should be in a position to consider both variables, namely, the standard deviation (sigma) and the deviation of average weight of a given group of cigarettes or the like from a desired or optimum average weight. This is particularly important in a modern cigarette maker or an analogous rod forming machine which operates satisfactorily when the weight of unit lengths of the rod matches or closely approximates a selected average or minimum acceptable value. A quality control which relies solely on two statistical values is not satisfactory.